CN108344899B - Distributed base station and cable impedance measuring method - Google Patents
Distributed base station and cable impedance measuring method Download PDFInfo
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- CN108344899B CN108344899B CN201710054202.8A CN201710054202A CN108344899B CN 108344899 B CN108344899 B CN 108344899B CN 201710054202 A CN201710054202 A CN 201710054202A CN 108344899 B CN108344899 B CN 108344899B
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Abstract
The embodiment of the invention provides a distributed base station and a cable impedance measuring method, wherein the distributed base station comprises a power supply, a remote radio unit and an impedance measuring circuit, wherein the power supply is connected with the remote radio unit through a cable and used for supplying power to the remote radio unit; the impedance measuring circuit is electrically connected with the output filter circuit of the power supply and is used for switching the output capacitor of the power supply from a first capacitance value to a second capacitance value, acquiring an alternating voltage component output by the power supply and an alternating current component flowing through the cable when the output capacitor of the power supply is the second capacitance value, and calculating the impedance of the cable according to the alternating voltage component and the alternating current component; when the output capacitor is the second capacitance value, the output voltage of the power supply contains an alternating voltage component. The distributed base station and the cable impedance measuring method can realize the online measurement of the cable impedance.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a distributed base station and a cable impedance measuring method.
Background
A communication base station is an over-the-road facility for providing wireless communication services for a user handset, wherein a Remote Radio Unit (RRU) is an important device of the communication base station. Currently, RRUs typically use cables to draw power from a power supply. However, the cable presents a certain impedance ZLThe impedance value is proportional to the distance. Current I flowing through cable in communication power supply systemLUsually large and therefore the cable voltage drop av caused by the cable impedance has to be taken into account. Power supply terminal output voltage VSRRU end input voltage VRAnd the cable voltage drop Δ V satisfies the following relation: vR＝VS-ΔV。
Currently, the output voltage of most communication power supply terminals is a fixed value, and the load power of the RRU is variable. Therefore, in order to ensure that the input voltage of the power supply end reaches the input voltage of the RRU after passing through the cable, the requirement of the input voltage for normal operation of the RRU can be met, the appropriate cable diameter and length need to be selected to ensure that the cable voltage drop is within the allowable range. Therefore, it is important for the RRU to know the information of the cable voltage drop.
With the increase of the power requirement of the RRU, the power supply current flowing through the cable increases sharply, so that the voltage drop and power consumption of the cable increase sharply, and the problems of low power supply efficiency, limited remote distance of the RRU, even low RRU input voltage, and the like are caused. In order to solve the problems, the output voltage of the power supply end can be dynamically adjusted according to the voltage drop of the cable, so that the input voltage of the RRU is always kept at the upper limit value of the operating voltage of the RRU, and the negative influence caused by the power loss of the cable and the voltage drop of the cable is reduced to the maximum extent. To achieve dynamic voltage regulation, the impedance of the cable must be obtained.
Commonly used methods for measuring the impedance of a cable include the following: (1) and (4) direct measurement, namely, directly measuring the two ends of the cable by using an impedance measuring instrument to obtain impedance. The method has the defects that the measurement can be carried out only before the cable is laid, and the measurement cannot be carried out on the constructed cable. (2) The power supply end is matched with the RRU end, namely the RRU end input voltage V is obtained by utilizing a communication means between the power supply end and the RRURAnd then measuring the output voltage V of the power supply endSWith current I flowing through the cableLAnd further calculating the cable impedance according to ohm's law: zL＝(VS-VR)/IL. The disadvantage of this method is that RRUs must be used that can communicate with the power supply system, which is not possible with conventional RRUs. (3) Assuming that the RRU power is constant, measuring the output voltage V of two power supply endsS1、VS2And a corresponding output current IS1、IS2If the instantaneous power of the RRUs corresponding to the two groups of measurement data is the same, calculating to obtain the cable impedance through a formula: zL＝(VS·IS-VR·IR)/(IS 2-IR 2). The disadvantage of this method is that the actual load of the RRU is variable, and calculating the impedance according to this formula causes large calculation errors.
Disclosure of Invention
The embodiment of the invention provides a distributed base station and a cable impedance measuring method, which aim to realize online measurement of cable impedance between a power supply of the distributed base station and a radio remote unit under the condition that the radio remote unit does not need to perform communication coordination, simplify the implementation mode of cable impedance measurement and reduce the measurement cost.
A first aspect of an embodiment of the present invention provides a distributed base station, including a power supply, a remote radio unit, and an impedance measurement circuit, where the power supply is connected to the remote radio unit through a cable, and is configured to supply power to the remote radio unit; the impedance measuring circuit is electrically connected with the output filter circuit of the power supply and is used for switching the output capacitor of the power supply from a first capacitance value to a second capacitance value, acquiring an alternating voltage component output by the power supply and an alternating current component flowing through the cable when the output capacitor of the power supply is the second capacitance value, and calculating the impedance of the cable according to the alternating voltage component and the alternating current component; when the output capacitor is the second capacitance value, the output voltage of the power supply contains an alternating voltage component.
In the distributed base station, an adjustable output filter circuit is arranged for the power supply, and an impedance measurement circuit is used for switching an output capacitor provided for the power supply by the output filter circuit from a first capacitance value to a second capacitance value smaller than the first capacitance value, so that the output voltage of the power supply comprises an alternating voltage component, the impedance measurement circuit is used for obtaining the alternating voltage component output by the power supply and the alternating current component flowing through the cable, and the impedance of the cable can be calculated according to the alternating voltage component and the alternating current component. In the calculation process of the cable impedance, a power supply is not required to be communicated with the remote radio unit, the instantaneous power of the remote radio unit is not required to be kept unchanged, the collection of alternating current components and the impedance calculation can be completed only by switching of the output capacitance value of a simple power supply end, an additional power supply is not required to participate, and the cost is low.
In one embodiment, the output filter circuit includes a first filter capacitor, a second filter capacitor and a resistor, the first filter capacitor is connected in parallel between the positive output end and the negative output end of the power supply, one end of the second filter capacitor is connected to the positive output end of the power supply, and the other end of the second filter capacitor is connected to the negative output end of the power supply through the resistor, wherein the capacitance value of the first filter capacitor is smaller than the capacitance value of the second filter capacitor.
In one embodiment, the impedance measuring circuit comprises a voltage sampling circuit, a current sampling circuit, a controllable switch tube and a controller; the voltage sampling circuit is electrically connected with the positive output end, the negative output end and the controller of the power supply and is used for acquiring an alternating voltage component output by the power supply when the output capacitor of the power supply is a second capacitance value; the current sampling circuit is electrically connected with the cable and the controller and is used for acquiring an alternating current component flowing through the cable when the output capacitor of the power supply is a second capacitance value; the controllable switch tube is connected with the resistor in parallel and is electrically connected with the controller; the controller is used for controlling the on-off of the controllable switching tube, reading the alternating voltage component and the alternating current component under the state that the controllable switching tube is switched off, and calculating the impedance of the cable according to the alternating voltage component and the alternating current component.
The controllable switch tube can be switched on or off under the control of the controller, and simultaneously the controllable switch tube is connected with the resistor in the output filter circuit in parallel, so that the resistor can be bypassed out of the output filter circuit by controlling the controllable switch tube to be switched on, or the resistor can be switched in the output filter circuit by controlling the controllable switch tube to be switched off. Meanwhile, because the capacitance value of the first filter capacitor is smaller than that of the second filter capacitor, when the controllable switch tube is switched off, the resistor has a larger impedance effect on an alternating-current voltage component output by the power supply, so that the alternating-current filtering capability of the second filter capacitor is reduced, namely the capacitance value of the whole output capacitor of the power supply is reduced; when the controllable switch tube is turned on, the resistor is bypassed, the filtering performance of the second filter capacitor is not affected, and the output capacitance value of the power supply is the parallel capacitance value of the first filter capacitor and the second filter capacitor, which is much larger than the output capacitance value when the controllable switch tube is turned off. Therefore, the switching of the output capacitance value of the power supply can be realized through the switching of the on-state or off-state of the controllable switch tube, so that the size of an alternating voltage component in the output voltage of the power supply can be conveniently controlled, the size of the required alternating voltage and alternating current component can be adjusted according to the sampling precision requirements of the voltage sampling circuit and the current sampling circuit, and the accuracy of impedance measurement is improved.
In an embodiment, the voltage sampling circuit includes a first dc blocking circuit, a filter circuit and a first differential amplifier circuit, the first dc blocking circuit and the filter circuit are connected to a positive output terminal and a negative output terminal of the power supply, and are configured to filter a dc voltage component from an output voltage of the power supply and retain an ac voltage component, and the first differential amplifier circuit is electrically connected to the first dc blocking circuit, the filter circuit and the controller, and is configured to differentially amplify the ac voltage component and output the amplified ac voltage component to the controller.
In an embodiment, the current sampling circuit includes a sampling resistor, a second blocking circuit, a filter circuit, and a second differential amplifier circuit, the sampling resistor is connected in series to the cable, the second blocking circuit and the filter circuit are connected to two ends of the sampling resistor, and are configured to obtain an ac voltage formed at two ends of the sampling resistor, the second differential amplifier circuit is electrically connected to the second blocking circuit, the filter circuit, and the controller, and is configured to output the ac voltage to the controller after performing differential amplification, and the controller calculates an ac current component flowing through the cable according to a resistance value of the sampling resistor and an ac voltage component at two ends of the sampling resistor.
It can be understood that the dc blocking circuit, the filter circuit and the differential amplifier circuit are arranged in the voltage sampling circuit and the current sampling circuit, so that an alternating current voltage component and an alternating current component can be well extracted from voltage and current signals output by the power supply, and the alternating current voltage component and the alternating current component are amplified by the differential amplifier and then output to the controller, so that the controller can calculate the cable impedance according to the filtered and amplified alternating current voltage component and alternating current component, and the calculation accuracy of the cable impedance can be effectively improved.
In one embodiment, when the controllable switch is in the on state, the resistor is bypassed by the controllable switch, the first filter capacitor is connected in parallel with the second filter capacitor, and the output capacitor of the power supply has a first capacitance value equal to a parallel capacitance value of the first filter capacitor and the second filter capacitor.
In an embodiment, when the controllable switch is in an off state, the resistor is configured to present an impedance effect to an ac voltage component output by the power supply, and an ac current component flowing through the second filter capacitor is reduced, where the output capacitor of the power supply is a second capacitance value, and the second capacitance value is equal to an equivalent capacitance value of the second filter capacitor connected in series with the resistor and then connected in parallel with the first filter capacitor.
In one embodiment, the controller calculates the impedance of the cable from the alternating voltage component and the alternating current component, including:
obtaining a fundamental wave amplitude of the alternating voltage component, a fundamental wave amplitude of the alternating current component, a phase difference and an angular frequency of the alternating voltage component and the alternating current component through discrete Fourier transform;
and calculating the impedance of the cable according to the fundamental wave amplitude of the alternating voltage component, the fundamental wave amplitude of the alternating current component, the phase difference and the angular frequency of the alternating voltage component and the alternating current component.
In one embodiment, the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiS△ phi is the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, omega is the angular frequency of the alternating voltage component and the alternating current component, R is the fundamental amplitude of the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable.
In one embodiment, the remote radio unit includes an input filter capacitor connected in parallel between a positive power input terminal and a negative power input terminal of the remote radio unit, and an impedance of the input filter capacitor to the ac voltage component is zero.
The input filter capacitor of the radio remote unit is set to be zero in impedance of the alternating voltage component, so that main voltage drop of the alternating voltage component output by the power supply can be formed by equivalent impedance of the cable, influence on a cable impedance measurement result due to change of instantaneous power of the radio remote unit is prevented, and impedance measurement precision is improved.
In one embodiment, the resistor is further configured to filter out transient current surges caused by voltage changes of the second filter capacitor when the controllable switch tube is turned on or off.
A second aspect of an embodiment of the present invention provides a method for measuring an impedance of a cable connected between a power supply and a load, including: switching an output capacitor of a power supply from a first capacitance value to a second capacitance value, wherein the second capacitance value is smaller than the first capacitance value, and when the output capacitor is the second capacitance value, an output voltage of the power supply comprises an alternating-current voltage component; acquiring an alternating current voltage component output by the power supply and an alternating current component flowing through the cable; calculating the impedance of the cable based on the alternating voltage component and the alternating current component.
In one embodiment, the second capacitance value is at least one order of magnitude less than the first capacitance value.
According to the cable impedance measuring method, the output capacitor of the power supply is switched from the first capacitance value to the second capacitance value which is far smaller than the first capacitance value, so that a larger alternating voltage component and alternating current component exist in the output of the power supply, the impedance of the cable can be calculated by obtaining the alternating voltage component and the alternating current component, the whole measuring process does not need to be communicated with a load end, and the power supply of a system does not need to be interrupted.
In one embodiment, said calculating the impedance of said cable from said alternating voltage component and said alternating current component comprises: obtaining a fundamental wave amplitude of the alternating voltage component, a fundamental wave amplitude of the alternating current component, a phase difference and an angular frequency of the alternating voltage component and the alternating current component through discrete Fourier transform; and calculating the impedance of the cable according to the fundamental wave amplitude of the alternating voltage component, the fundamental wave amplitude of the alternating current component, the phase difference and the angular frequency of the alternating voltage component and the alternating current component.
In one embodiment, the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiS△ phi is the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, omega is the angular frequency of the alternating voltage component and the alternating current component, R is the fundamental amplitude of the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable.
In one embodiment, the load is a remote radio unit, and the voltage drop of the alternating voltage component across the remote radio unit is zero.
The voltage drop of the alternating voltage component on the remote radio unit is controlled to be zero, so that the main voltage drop of the alternating voltage component output by the power supply is formed by the equivalent impedance of the cable, the influence on the cable impedance measurement result due to the change of the instantaneous power of the remote radio unit is prevented, and the impedance measurement precision is improved.
In one embodiment, after calculating the impedance of the cable based on the alternating voltage component and the alternating current component, the method further comprises: and switching the output capacitor of the power supply from the second capacitance value to the first capacitance value.
It can be understood that after impedance measurement is accomplished, through switching the output capacitance of power back to first electric capacity by the second electric capacity, can guarantee that the power can not have great alternating current component output at normal studio to can not cause great alternating current filtering burden to the input filter capacitance of load end, can effectively promote load end input filter capacitance's life, and then guarantee whole distal end power supply system's stable work.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and the description of the embodiments of the present invention will be briefly described below.
Fig. 1 is a schematic structural diagram of a distributed base station according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a power supply circuit of a remote radio unit of a distributed base station according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an AC signal equivalent circuit of the power supply circuit of FIG. 2;
FIG. 4 is a schematic circuit diagram of a cable impedance measurement method according to an embodiment of the present invention;
fig. 5 is a schematic flow chart of a cable impedance measurement method according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described below with reference to the accompanying drawings.
Referring to fig. 1, in an embodiment of the present invention, a distributed base station 100 is provided, which includes a power supply 110, a Baseband processing Unit (BBU) 130, a Remote Radio Unit (RRU) 150, and an impedance measurement circuit 170. The power supply 110 is connected to the remote radio unit 150 through a cable, and is configured to supply power to the remote radio unit 150. The power source 110 may include a positive output end and a negative output end, the remote radio unit 150 may include a positive input end and a negative input end, the positive output end of the power source 110 is connected to the positive input end of the remote radio unit 150 through a cable 1, and the negative output end of the power source 110 is connected to the negative input end of the remote radio unit 150 through a cable 2. The power supply 110 includes an output filter circuit 111, and the output filter circuit 111 is connected between the positive output end and the negative output end of the power supply 110, and is configured to provide an output capacitor for the power supply 110. The impedance measuring circuit 170 is electrically connected to the output filter circuit 111 of the power supply 110, and configured to switch an output capacitance of the power supply 110 from a first capacitance value to a second capacitance value, obtain an alternating voltage component output by the power supply and an alternating current component flowing through the cable when the output capacitance of the power supply 110 is the second capacitance value, and calculate an impedance of the cable according to the alternating voltage component and the alternating current component. When the second capacitance value is smaller than the first capacitance value and the output capacitance is the second capacitance value, the output voltage of the power supply 110 includes an ac voltage component.
It is understood that the impedance measurement circuit 170 may be connected to the positive output terminal and the negative output terminal of the power supply 110, so as to facilitate the collection of the alternating voltage component output by the power supply 110. Meanwhile, the impedance measuring circuit 170 may include a sampling resistor Ri connected in series to the cable 1 or the cable 2, and the impedance measuring circuit 170 may calculate an alternating current component flowing through the cables 1 and 2 by reading an alternating voltage component across the sampling resistor Ri. After the alternating voltage component output by the power supply and the alternating current component flowing through the cable are collected, the impedance of the cable can be calculated according to the alternating voltage component and the alternating current component.
With the increase of the power requirement of the RRU, the power supply current flowing through the cable increases sharply, so that the voltage drop and power consumption of the cable increase sharply, and the problems of low power supply efficiency, limited remote distance of the RRU, even low input voltage of the RRU, resulting in under-voltage protection and the like may be caused. In order to ensure the normal operation of the RRU, in this embodiment, the impedance of the cable is measured by the impedance measurement circuit 170, so that the voltage drop of the cable can be calculated according to the impedance of the cable, and the output voltage of the power supply terminal is dynamically adjusted according to the voltage drop of the cable, so that the input voltage of the RRU is always kept at the upper limit value of the operating voltage of the RRU, and negative effects caused by the power loss of the cable and the voltage drop of the cable are minimized.
In this embodiment, for convenience of describing the principle of calculating the cable impedance according to the alternating voltage component and the alternating current component, the power supply circuit of the remote rf unit 150 of the distributed base station 100 is simplified to a circuit structure as shown in fig. 2. The power supply 110 is simplified into a Boost (Boost) circuit topology, which includes a dc input voltage Vin, a switching tube Q, an equivalent internal inductance Lin, a diode D, and an output capacitor Co, and the cable 1 is simplified into an equivalent resistor Rline1And equivalent inductance Lline1To simplify the cable 2 to an equivalent resistance Rline2And equivalent inductance Lline2And simplifies the remote radio unit 150 into a load resistor RLAnd an input filter capacitor CLThe parallel circuit of (1). It is understood that the simplified circuit structure shown in fig. 2 is only for illustrating the principle of the power supply circuit of the radio remote unit, and does not form a structural limitation on the power supply circuit, for example, the power supply 110 is not limited to a Boost circuit topology, and may also be a Buck (Buck) circuit topology, a Buck-Boost (Buck-Boost) circuit topology, or the like.
Because the RRU is powered by the direct current, when the power supply 110 normally powers the RRU, the output capacitor Co filters the alternating current component output by the power supply, and at this time, the output capacitor Co needs a larger first capacitance value to meet the requirement of alternating current filtering, so as to ensure that the alternating current component output by the power supply can be completely filtered. In this embodiment, to measure the cable impedance by the ac component flowing through the cable, the capacitance value of the output capacitor Co may be switched from a first larger capacitance value to a second capacitance value that is much smaller than the first capacitance value, and in this embodiment, the second capacitance value is at least one order of magnitude smaller than the first capacitance value. At this time, since the ac filtering capability of the output capacitor Co is sharply reduced, the ac component of the power output cannot be completely filtered, that is, the output voltage of the power supply 110 includes an ac voltage component, so that an ac current component flows through the cable.
Meanwhile, the input filter capacitor C of the radio remote unitLUsually an electrolytic capacitor with a large capacitance value, the input filter capacitor CLThe impedance to the alternating voltage component is zero, so that the input filter capacitors C are connected in parallelLAnd a load resistance RLThe alternating current component is straight-through, i.e. the voltage drop of the alternating current component over the RRU is zero. That is, the impedance of the ac component of the power supply output is mainly composed of the equivalent resistance and the equivalent inductance of the cable. At this time, the ac signal equivalent circuit of the power supply circuit of the remote rf unit shown in fig. 2 can be represented as the circuit configuration shown in fig. 3. Wherein v issAn alternating voltage component, i, output by the power supplysFor the alternating current component flowing through the cable, RlineAnd LlineRespectively the equivalent resistance and the equivalent inductance of the cable.
The alternating voltage component v is obtained after collectionsAnd an alternating current component isThen, the AC voltage component v is calculated by adopting discrete Fourier transformsFundamental amplitude A ofvSAnd an alternating current component isFundamental amplitude A ofiSComponent v of alternating voltagesAnd an alternating current component isPhase difference between
And corresponding angular frequency ω, the cable impedance can be calculated by the following equation:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiS△ phi is the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, omega is the angular frequency of the alternating voltage component and the alternating current component, R is the fundamental amplitude of the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable. Further, according to the principle that the real part and the imaginary part are respectively equal, the method can obtain
As can be seen from the above analysis, the output voltage of the power supply 110 can include an ac voltage component by switching the output capacitance of the power supply 110 from a first capacitance value to a second capacitance value that is much smaller than the first capacitance value, and the ac voltage component is superimposed on the dc voltage component and forms an ac loop through the cable and the RRU. However, if the output of the power supply 110 contains a large ac component for a long time, a large filtering burden is imposed on the input filter capacitor of the RRU, which affects the service life of the RRU. Therefore, in order to ensure the performance of the entire distributed base station, the impedance measurement circuit 170 and the output filter circuit 111 of the power supply 110 need to be designed, so that the impedance measurement circuit 170 can switch the output capacitance provided by the output filter circuit 111 from a first capacitance value to a second capacitance value which is much smaller than the first capacitance value during impedance measurement, and the impedance measurement circuit 170 can switch the output capacitance provided by the output filter circuit 111 from the second capacitance value to the first capacitance value after impedance measurement is completed, thereby ensuring that the power supply 110 does not have an excessive ac component output during normal operation, and reducing the filtering burden of the input filter capacitor of the RRU.
Referring to fig. 4, in an embodiment, the output filter circuit 111 includes a first filter capacitor Co1, a second filter capacitor Co2 and a resistor Rc, the first filter capacitor Co1 is connected in parallel between the positive output terminal and the negative output terminal of the power supply 110, one end of the second filter capacitor Co2 is connected to the positive output terminal of the power supply 110, and the other end is connected to the negative output terminal of the power supply 110 through the resistor Rc. Wherein the capacitance value of the first filter capacitor Co1 is much smaller than that of the second filter capacitor Co 2. In this embodiment, the capacitance value of the first filter capacitor Co1 is at least one order of magnitude smaller than that of the second filter capacitor Co 2.
The impedance measuring circuit 170 includes a voltage sampling circuit 171, a current sampling circuit 173, a controllable switch tube Qc and a controller 175; the voltage sampling circuit 171 is electrically connected to the positive output terminal and the negative output terminal of the power supply 110 and the controller 175, and is configured to obtain an alternating current voltage component output by the power supply 110 when an output capacitor of the power supply 110 is a second capacitance value; the current sampling circuit 173 is electrically connected to the cable and the controller 175, and is configured to obtain an alternating current component flowing through the cable when the output capacitor of the power supply 110 is a second capacitance value; the controllable switch tube Qc is connected in parallel with the resistor Rc and electrically connected to the controller 175; the controller 175 is configured to control the controllable switching tube Qc to be turned on or off, read the ac voltage component and the ac current component when the controllable switching tube Qc is turned off, and calculate the impedance of the cable according to the ac voltage component and the ac current component.
The voltage sampling circuit 171 may include a first dc blocking and filtering circuit 1711 and a first differential amplifying circuit 1713, where the first dc blocking and filtering circuit 1711 is connected to the positive output terminal and the negative output terminal of the power supply 110, and is configured to filter a dc voltage component from the output voltage of the power supply 110 and retain an ac voltage component, and the first differential amplifying circuit 1713 is electrically connected to the first dc blocking and filtering circuit 1711 and the controller 175, and is configured to differentially amplify the ac voltage component and output the amplified ac voltage component to the controller 175. The current sampling circuit 173 may include a sampling resistor Ri, a second blocking and filtering circuit 1731, and a second differential amplifier circuit 1733, where the sampling resistor Ri is connected in series to the cable, the second blocking and filtering circuit 1731 is connected to two ends of the sampling resistor Ri, and is configured to obtain an ac voltage formed at two ends of the sampling resistor Ri, the second differential amplifier circuit 1733 is electrically connected to the second blocking and filtering circuit 1731 and the controller 175, and is configured to perform differential amplification on the ac voltage and output the amplified ac voltage to the controller 175, and then the controller 175 calculates an ac current component flowing through the cable according to a resistance value of the sampling resistor Ri and ac voltage components at two ends of the sampling resistor Ri. It is understood that the first dc blocking and filtering circuit 1711, the first differential amplifying circuit 1713, the second dc blocking and filtering circuit 1731, and the second differential amplifying circuit may be implemented by dc blocking and filtering circuits and differential amplifying circuits commonly used in the art, and will not be described in detail herein.
It is understood that, when the controllable switch Qc is in the on state, the resistor Rc is bypassed by the controllable switch Qc, the first filter capacitor Co1 is connected in parallel with the second filter capacitor Co2, and the output capacitor of the power supply 110 has a first capacitance value, which is equal to the parallel capacitance value of the first filter capacitor and the second filter capacitor.
When the controllable switch tube Qc is in the off state, the resistor Rc is used to present an impedance effect to the ac voltage component output by the power supply 110, the ac current component flowing through the second filter capacitor Co2 is reduced, the output capacitor of the power supply 110 is a second capacitance value, and the second capacitance value is equal to an equivalent capacitance value of the second filter capacitor Co2 connected in series with the resistor Rc and then connected in parallel with the first filter capacitor Co 1.
It can be understood that the capacitance value of the first filter capacitor Co1 is much smaller than that of the second filter capacitor Co 2. When the power supply 110 works normally and the resistor Rc is bypassed by the controllable switch tube Qc, the capacitance value of the output capacitor of the power supply 110 is equal to the parallel capacitance value of the first filter capacitor Co1 and the second filter capacitor Co2, so that the capacitance value of the output capacitor of the power supply 110 is large, most of the ac component output by the power supply 110 is filtered by the first filter capacitor Co1 and the second filter capacitor Co2, and thus the power supply 110 is prevented from outputting an excessive ac component to cause a large filtering burden on the input filter capacitor of the RRU, and the normal operation of the power supply 110 and the RRU is ensured.
When the cable impedance measurement is needed, the controllable switching tube Qc is disconnected, and the resistor Rc is connected to the output filter circuit 111, so that the series branch formed by the second filter capacitor Co2 and the resistor Rc is coupled to the ac voltage component v due to the relatively large resistance of the resistor RcsThe impedance of the second filter capacitor Co2 is large, so that the ac filtering capability of the second filter capacitor Co2 is sharply reduced, and meanwhile, the ac filtering capability of the whole output filter circuit 111 is reduced because the capacitance value of the first filter capacitor Co1 is much smaller than that of the second filter capacitor Co2, so that the output voltage of the power supply 110 includes a large ac voltage component vsAnd forming an alternating current component i on said cables. It can be understood that the resistor Rc is also used for filtering out transient current surge caused by voltage change of the second filter capacitor Co2 when the controllable switch tube Qc is turned on or off.
In one embodiment, the controller 110 calculates the impedance of the cable based on the alternating voltage component and the alternating current component, including:
the controller 110 obtains a fundamental amplitude of the alternating voltage component, a fundamental amplitude of the alternating current component, a phase difference between the alternating voltage component and the alternating current component, and an angular frequency through discrete fourier transform;
the controller 110 calculates the impedance of the cable based on the fundamental amplitude of the alternating voltage component, the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, and the angular frequency.
In this embodiment, the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiS△ phi is the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, omega is the angular frequency of the alternating voltage component and the alternating current component, R is the fundamental amplitude of the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable.
In this embodiment, the output filter circuit 111 of the power supply 110 is designed to be formed by connecting the second filter capacitor Co2 and the resistor Rc in series and then connecting the second filter capacitor Co2 and the first filter capacitor Co1 in parallel, and the resistor Rc is bypassed or connected to the output filter circuit 111 by turning on or off the controllable switch tube Qc, so that the output capacitance of the output filter circuit 111 can be switched between a first capacitance and a second capacitance much smaller than the first capacitance. When the cable impedance measurement is required, the controller 175 controls the controllable switch Qc to be turned off, so that the output capacitance of the power supply 110 is switched to a second smaller capacitance value, and it is ensured that a larger alternating voltage component and an alternating current component exist in the output of the power supply 110, so that the alternating voltage component is collected by the voltage sampling circuit 171, the alternating current component is collected by the current sampling circuit 173, and the controller 175 calculates the cable impedance according to the alternating voltage component and the alternating current component. After the cable impedance measurement is completed, the controller 175 may control the controllable switch Qc to be turned on, so that the output capacitor of the power supply 110 is switched to a larger first capacitance value, thereby preventing the normal operating room from outputting a larger ac component to cause a larger filtering burden on the input filter capacitor of the RRU, which may affect the service life of the input filter capacitor of the RRU. It can be understood that after the cable impedance is measured, the controller 175 can also control the power supply 110 to adjust the output power, so that the output power can still meet the normal power requirement of the RRU after the power lost by the cable impedance is extracted, thereby improving the communication performance of the entire distributed base station.
Referring to fig. 5, in an embodiment of the present invention, a cable impedance measuring method is provided for measuring the impedance of a cable connected between a power source and a load, the method at least includes the following steps:
step 501: switching an output capacitor of a power supply from a first capacitance value to a second capacitance value, wherein the second capacitance value is smaller than the first capacitance value, and when the output capacitor is the second capacitance value, an output voltage of the power supply comprises an alternating-current voltage component;
step 502: acquiring an alternating current voltage component output by the power supply and an alternating current component flowing through the cable;
step 503: calculating the impedance of the cable based on the alternating voltage component and the alternating current component.
In one embodiment, the second capacitance value is at least one order of magnitude less than the first capacitance value.
In one embodiment, said calculating the impedance of said cable from said alternating voltage component and said alternating current component comprises:
obtaining a fundamental wave amplitude of the alternating voltage component, a fundamental wave amplitude of the alternating current component, a phase difference and an angular frequency of the alternating voltage component and the alternating current component through discrete Fourier transform;
and calculating the impedance of the cable according to the fundamental wave amplitude of the alternating voltage component, the fundamental wave amplitude of the alternating current component, the phase difference and the angular frequency of the alternating voltage component and the alternating current component.
In one embodiment, the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiS△ phi is the fundamental amplitude of the alternating current component, the phase difference between the alternating voltage component and the alternating current component, omega is the angular frequency of the alternating voltage component and the alternating current component, R is the fundamental amplitude of the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs said electricityEquivalent inductance of the cable.
In one embodiment, the load is a remote radio unit, and the voltage drop of the alternating voltage component across the remote radio unit is zero.
In one embodiment, after calculating the impedance of the cable based on the alternating voltage component and the alternating current component, the method further comprises: and switching the output capacitor of the power supply from the second capacitance value to the first capacitance value.
It can be understood that specific implementation of each step of the cable impedance measurement method according to this embodiment may also refer to the related description in the embodiments shown in fig. 1 to fig. 4, and details are not described here again.
It can be understood that the cable impedance measurement method described in this embodiment is not limited to measuring the impedance of the cable between the power supply of the distributed base station and the RRU, but may be applied to measuring the cable impedance between the power supply end and the load end in any remote power supply system, and only needs to ensure that the main voltage drop of the ac component included in the power output is formed by the equivalent impedance on the cable, and the input capacitance of the load end is large, so that the impedance of the ac component output by the power supply is close to zero.
According to the cable impedance measuring method, the output capacitor of the power supply is switched from the first capacitance value to the second capacitance value which is far smaller than the first capacitance value, so that a larger alternating voltage component and an alternating current component exist in the output of the power supply, the impedance of the cable can be calculated by obtaining the alternating voltage component and the alternating current component, the whole measuring process does not need to be communicated with a load end, and the system power supply does not need to be interrupted. In addition, after impedance measurement is accomplished, through switching the output capacitance of power back to first electric capacity by the second electric capacity, can guarantee that the power can not have great alternating current component output at normal studio to can not cause great alternating current filtering burden to the input filter capacitance of load end, can effectively promote the life of load end input filter capacitance, and then guarantee whole distal end power supply system's stable work.
Claims (14)
1. A distributed base station is characterized by comprising a power supply, a remote radio unit and an impedance measuring circuit, wherein the power supply is connected with the remote radio unit through a cable and used for supplying power to the remote radio unit; the impedance measuring circuit is electrically connected with the output filter circuit of the power supply and is used for switching the output capacitor of the power supply from a first capacitance value to a second capacitance value, acquiring an alternating voltage component output by the power supply and an alternating current component flowing through the cable when the output capacitor of the power supply is the second capacitance value, and calculating the impedance of the cable according to the alternating voltage component and the alternating current component; wherein, when the second capacitance value is smaller than the first capacitance value and the output capacitance is the second capacitance value, the output voltage of the power supply comprises an alternating voltage component,
wherein the second capacitance value is at least one order of magnitude less than the first capacitance value.
2. The distributed base station of claim 1, wherein the output filter circuit comprises a first filter capacitor, a second filter capacitor and a resistor, the first filter capacitor is connected in parallel between the positive output terminal and the negative output terminal of the power supply, one end of the second filter capacitor is connected to the positive output terminal of the power supply, the other end of the second filter capacitor is connected to the negative output terminal of the power supply through the resistor, and wherein a capacitance value of the first filter capacitor is smaller than a capacitance value of the second filter capacitor.
3. The distributed base station of claim 2, wherein the impedance measurement circuit comprises a voltage sampling circuit, a current sampling circuit, a controllable switching tube, and a controller; the voltage sampling circuit is electrically connected with the positive output end, the negative output end and the controller of the power supply and is used for acquiring an alternating voltage component output by the power supply when the output capacitor of the power supply is a second capacitance value; the current sampling circuit is electrically connected with the cable and the controller and is used for acquiring an alternating current component flowing through the cable when the output capacitor of the power supply is a second capacitance value; the controllable switch tube is connected with the resistor in parallel and is electrically connected with the controller; the controller is used for controlling the on-off of the controllable switching tube, reading the alternating voltage component and the alternating current component under the state that the controllable switching tube is switched off, and calculating the impedance of the cable according to the alternating voltage component and the alternating current component.
4. The distributed base station of claim 3, wherein the controllable switch is in an on state, the resistor is bypassed by the controllable switch, the first filter capacitor is connected in parallel with the second filter capacitor, and the output capacitor of the power supply has a first capacitance value equal to a parallel capacitance value of the first filter capacitor and the second filter capacitor.
5. The distributed base station of claim 3, wherein the controllable switch is configured to, in an off state, present an impedance to an ac voltage component output by the power supply, and reduce an ac current component flowing through the second filter capacitor, and the output capacitor of the power supply has a second capacitance value equal to an equivalent capacitance value of the second filter capacitor connected in series with the resistor and then connected in parallel with the first filter capacitor.
6. The distributed base station of claim 3 wherein said controller calculates said cable impedance from said alternating voltage component and said alternating current component, comprising:
obtaining a fundamental wave amplitude of the alternating voltage component, a fundamental wave amplitude of the alternating current component, a phase difference and an angular frequency of the alternating voltage component and the alternating current component through discrete Fourier transform;
and calculating the impedance of the cable according to the fundamental wave amplitude of the alternating voltage component, the fundamental wave amplitude of the alternating current component, the phase difference and the angular frequency of the alternating voltage component and the alternating current component.
7. The distributed base station of claim 6, wherein the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiSIs a fundamental amplitude of the alternating current component, Δ φ is a phase difference of the alternating voltage component and the alternating current component, ω is an angular frequency of the alternating voltage component and the alternating current component, R is a phase difference of the alternating voltage component and the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable.
8. The distributed base station of claim 1, wherein the remote radio unit includes an input filter capacitor connected in parallel between a positive power input and a negative power input of the remote radio unit, the input filter capacitor having zero impedance to the ac voltage component.
9. The distributed base station of claim 3, wherein the resistor is further configured to filter transient current surges due to voltage variations in the second filter capacitor when the controllable switching tube is turned on or off.
10. A cable impedance measurement method for measuring an impedance of a cable connected between a power source and a load, comprising:
switching an output capacitor of a power supply from a first capacitance value to a second capacitance value, wherein the second capacitance value is smaller than the first capacitance value, when the output capacitor is the second capacitance value, an output voltage of the power supply contains an alternating-current voltage component, and the second capacitance value is smaller than the first capacitance value by at least one order of magnitude;
acquiring an alternating current voltage component output by the power supply and an alternating current component flowing through the cable;
calculating the impedance of the cable based on the alternating voltage component and the alternating current component.
11. The method of claim 10, wherein said calculating the impedance of the cable from the alternating voltage component and the alternating current component comprises:
obtaining a fundamental wave amplitude of the alternating voltage component, a fundamental wave amplitude of the alternating current component, a phase difference and an angular frequency of the alternating voltage component and the alternating current component through discrete Fourier transform;
and calculating the impedance of the cable according to the fundamental wave amplitude of the alternating voltage component, the fundamental wave amplitude of the alternating current component, the phase difference and the angular frequency of the alternating voltage component and the alternating current component.
12. The method of claim 11, wherein the impedance of the cable is:
wherein A isvSIs the fundamental amplitude, A, of the AC voltage componentiSIs a fundamental amplitude of the alternating current component, Δ φ is a phase difference of the alternating voltage component and the alternating current component, ω is an angular frequency of the alternating voltage component and the alternating current component, R is a phase difference of the alternating voltage component and the alternating current componentlineIs the equivalent resistance, L, of the cablelineIs the equivalent inductance of the cable.
13. The method of claim 10, wherein the load is a remote radio unit and the voltage drop of the ac voltage component across the remote radio unit is zero.
14. The method of claim 10, wherein after calculating the impedance of the cable from the alternating voltage component and the alternating current component, the method further comprises:
and switching the output capacitor of the power supply from the second capacitance value to the first capacitance value.
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